The purpose of this project is to seek better understanding of the structure and function of the human gastrointestinal mucosa in health and in disease. The synthesis of chylomicrons, the metabolism of bile salts by intestinal mucosa, the effect of bile salts and detergents on water and electrolyte fluxes in intestinal segments, and the lumenal factors which influence oxalate absorption are under study. We shall continue our investigations of the pathogenesis of a variety of diseases involving the human gastrointestinal tract including: stasis syndrome, celiac sprue - dermatitis herpetiformis, erosive gastritis, graft versus host reaction, idiopathic inflammatory disease of the small and large bowel. We will also continue studies to define the diagnostic usefulness of blind peroral suction biopsy and endoscopic biopsy of the gastrointestinal tract. BIBLIOGRAPHIC REFERENCES: Perera, D.R., Weinstein, W.M., and Rubin, C.E.: The diagnostic usefulness of small bowel biopsy. Human Pathology 6:157-217, 1975. Saunders, D.R., Hedges J.R., Sillery, J., Esther, L., Matsumura, K. and Rubin, C.E.: Morphological and functional effects of bile salts on rat colon. Gastroenterology 68:1236-1245, 1975.